1. Field of the Invention
This invention relates generally to the convective application of heat in a medical setting by delivery of a bath of a thermally-controlled gaseous medium, such as warmed air, to a patient. More particularly, the invention pertains to the use of inflatable blankets and surgical drapes to control body temperature during a medical procedure, while providing access to the patient for medical purposes such as cardiac surgery.
2. Description of the Related Art
The construction and operation of inflatable thermal blankets for convective warming of patients is disclosed in commonly-assigned U.S. Pat. No. 4,572,188 entitled "AIRFLOW COVER FOR CONTROLLING BODY TEMPERATURE," and U.S. Pat. No. 5,405,371 entitled "THERMAL BLANKET". These two patents describe thermal blankets that include a plurality of communicating inflatable chambers and apertures that open through lower blanket surfaces into the chambers. When inflated with warmed air, the pressure of the air in the chambers causes the thermal blankets to inflate. The apertures that open through the bottoms of the thermal blankets exhaust the warmed air onto the patient. Therefore, these inflatable thermal blankets create an ambient environment about the patient, the thermal characteristics of which are determined by the temperature and pressure of the gaseous inflating medium. One use for an inflatable thermal blanket is the maintenance of patient normothermia during a medical procedure, such as surgery.
The typical inflatable thermal blanket covers all, or much of, the patient's body, and it is not always possible to simultaneously access the patient, for medical purposes, while the blanket lays over the patient and provides temperature regulation.
The difficuliy in providing patient access through an inflatable thermal blanket utilizing super atmospheric temperature controlled air is that such access interferes with the thermal regulation desired to be achieved by the blanket. This is especially significant during cardiac surgery when access must often be initially provided to the legs so that segments of a patient's leg veins can be removed and transplanted to the heart. In this respect, cardiac surgery is a progressive procedure, in that it progresses from an initial site (the legs), through intermediate sites (possibly), to a terminal site (the chest). Once the leg vein segments are removed, access to the legs is no longer required yet there is no ability to direct temperature controlled air to the leg area, unless a separate thermal blanket is placed over the legs. Placing a new thermal blanket over the legs, however, raises the issue of how to effectively attach and seal the blanket to the patient, without disrupting the procedure, so as to contain the temperature controlled air and achieve effective thermal regulation of the patient.
Accordingly, a need exists for a warming system that is capable of delivering a temperature-controlled airflow to a patient during a progressive medical procedure, such as cardiac surgery, so as to maintain the patient's body temperature at a desired level while simultaneously allowing initial access to one or more areas of the patient's body, following which the one or more areas can be covered for additional temperature control. What is required is a system that, while warming first portions of a patient's body, allows initial unimpaired medical access to, and subsequent temperature control of, other portions of the patient's body, without jeopardizing the patient's health or comfort during a medical procedure.